Fifty-one Jersey bull calves (5 ± 1 d old) were assigned to 1 of 3 milk replacers to determine the effects of increasing doses of n-3 fatty acids from fish oil on the acute phase response after an endotoxin challenge. All calves were fed a 22.5% crude protein and 18% lipid milk replacer (Calva Products, Acampo, CA) supplemented with an additional 2% fatty acids. Treatments differed only in the supplemental lipid source and included a 3:1 mix of corn and canola oils, a 1:1 blend of fish oil (Omega Proteins, Houston, TX) and the 3:1 mix of corn and canola oils, and fish oil only. On d 23, each calf was injected subcutaneously with 4 pg/kg of body weight of Salmonella Typhimurium endotoxin. Clinical, hematological, and biochemical parameters were measured at 0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 18, 24, and 72 h post endotoxin challenge. Endotoxin caused a dramatic rise in respiratory rate; feeding fish oil significantly attenuated the increase. Heart rate and rectal temperature were not affected by treatment. Feeding fish oil attenuated the change in serum iron concentration over time. Endotoxin caused severe hypoglycemia, reaching a nadir at 4 h. Calves supplemented with fish oil had reduced concentrations of serum glucose for 8 to 24 h. Furthermore, calves supplemented with fish oil alone had reduced serum insulin at 12, 28, and 24 h. In contrast, endotoxin caused an acute increase in blood urea nitrogen and nonesterified fatty acids; there were significant linear effects of fish oil on both blood urea nitrogen and nonesterified fatty acids. Serum triglycerides were elevated beginning at 12 h after the endotoxin challenge and returned to baseline values within 72 h. Fish oil suppressed the rise in triglycerides during this period, and the effect was linear with increasing fish oil. Serum concentrations of leptin decreased after the endotoxin challenge; however, the treatment did not influence the response. There was no treatment effect on serum aspartate aminotransferase or lactate dehydrogenase activity. Adding fish oil to milk replacer attenuated many aspects of the acute phase response, and the effect was linear in the range of 5 to 10% of the lipid replaced as fatty acids from fish oil. Adding fish oil might provide a better balance between a necessary versus an excessive acute phase response.
- Fish oil